Intervertebral disc prosthesis, surgical methods,  and fitting tools

ABSTRACT

An intervertebral disc prosthesis designed to be substituted for fibrocartilaginous discs ensures a connection between the vertebra of the vertebra column or the end of the latter. The prosthesis includes a pair of plates spaced from each other by a nucleus. The prosthesis has increased stability by providing the nucleus with a translation or rotation stop, or by inducing an angular correction between its plates contacting vertebra, or a combination of these characteristics. The stop includes pales external to the nucleus and contact surfaces perpendicular to their contact directions. Surgical methods and instrumentation for implanting the prosthesis are also described.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/476,565 filed Nov. 4, 2003, and issuing Feb. 5, 2008, asU.S. Pat. No. 7,326,250, which is a 35 U.S.C. § 371 application ofPCT/IB02/002998 filed May 3, 2002, which claims priority to FR 01/05982filed May 4, 2001. All of the foregoing documents are herebyincorporated by reference.

BACKGROUND

The present invention concerns an intervertebral disc prosthesisdesigned to be substituted for fibrocartilaginous discs ensuringconnection between the vertebra of the vertebral column or the end ofthe latter.

The intervertebral discs are formed from a deformable butnoncompressible element called “nucleus pulposus” containingapproximately 80% water, surrounded by several elastic fibrous layersconverging to maintain the nucleus, absorb part of the forces applied tothe entire disc and stabilize the articulation. These elements may oftenbe broken down or damaged by compression, displacement or wear and tear,following shocks, infections, exaggerated forces or simply over time.

The breakdown of this articulation element may cause intense pain andsignificant constraint in the patient. Beyond the surgery that consistedof blocking the deficient articulation and possibly purely and simplyremoving the damaged disc, a therapeutic route for the last twenty or soyears consists of surgically replacing the defective disc with afunctional prosthesis. However, the use of such a prosthesis requires adevice that is not very cumbersome, that supports significant forces, orhas a great sturdiness over time. Furthermore, the comfort of thepatients already affected by great and acute pain makes it desirable toarrange for a prosthesis that most faithfully reproduces the naturalpossibilities of movements and at the same time ensures the beststability possibility to the spinal column that is sometimes alreadydamaged.

The use of such a prosthesis therefore crucially depends on thestability that it allows the spinal column, as much during movements asduring static forces or lengthy constant position.

A certain number of prostheses have been proposed with a compressiblematerial base, with the goal of reproducing the kinematics of naturalmovement while reproducing its components and their characteristics ofshape or plasticity, as described in the patent FR 2 124 815 whichproposes a disc from elastomer material reinforced by a textilematerial. These devices present the drawback of a lifetime that is oftentoo limited and also suffer from drawbacks indeed due to thiselasticity. In fact, since the prosthesis is entirely compressible, aprogressive sliding of the prosthesis may be produced relative to thevertebra between which it is placed, which too often leads it to leaveits housing. The addition of anchoring pins does not allow sufficientremedy for this problem, because the micromovements permitted by thecompressibility of the material of the prosthesis also include avertical component, which too easily allows the pins to leave theirhousing with each movement.

Among the prostheses nor resting on the deformation of materials, a typeof prosthesis frequently used is described by the patent DE 30 23 353and is formed of a nucleus with the shape of a biconvex lens formingarticulation between two plates each presenting a cavity with a shapeapproximately complementary to the nucleus in their centre and on theirperimeter a shoulder retaining this nucleus. This arrangement presentsthe advantage by comparison to a more limited ball-and-socket joint ofusing significant contact surface, which largely decreases the wear andtear.

To incline one with the other on one side, the plates are articulated bytheir internal cavity on the edge of the nucleus of the side inquestion, but according to a rotation movement which, on the other sidemakes their edges move apart more than they were at rest. Thisseparating has a tendency to detach the vertebral plates on which theyare supported, which damages the surface of the vertebra at the siteswhere the plates have just anchored and again allows progressivedisplacement with risk of complete ejection of the prosthesis.

Another type of prosthesis described in patent FR 2 659 226 consists ofan upper plate presenting a concave face that comes to slide on anucleus in the form of a segment of a sphere, this nucleus beingimmobilized in a cavity of the lower plate. In this case, the rotationis done more satisfactorily from the point of view of space of theplates, but the sliding of the upper plate on a sphere whose centre islocated on the exterior of the prosthesis also causes lateraldisplacement which may be harmful as much to the kinematics of movementas to the organs present in the vicinity.

A solution is proposed in the patent FR 2 730 159 in the form of anucleus presenting two spherical faces, oriented in the same direction,and with different radius. The nucleus with cylindrical exterior slideson a convex surface belonging the lower plate and itself presents aconvex surface on the top, on which the upper plate slides. Because thenucleus is movable horizontally, it is in a position to move apart fromone side when the plates approach the other. However, this devicepresents the drawback of risking the complete ejection of the nucleusoutside the prosthesis, this drawback also existing in the devicedescribed by the patent DE 30 23 353).

In the goal of limiting the risks of ejection of the nucleus, thepatents WO 00 53 127, as well as U.S. Pat. No. 5,401,269 and U.S. Pat.No. 4,759,766 propose to provide a translation stop, produced indifferent ways.

In certain variants, a translation stop is disclosed in the form of arelief protruding from one contact surface of the nucleus and movable ina recess in the plate or inversely. This type of internal stop istherefore located on the interior of a contact or support surfacebetween nucleus and plate, and therefore decreases the available surfaceconsiderably. This decrease in support surface increases the stressesundergone by the materials, therefore the risks of wear and tear orstrain in creep or exceeding elastic limits. The separation between thesupport surface and housing receiving the stop may also risk marking thepiece which is supported above and damaging the latter.

In certain cases, such a central stop is provided with a noncircularshape, which in a certain extent allows the rotations of the nucleus tobe limited relative to the plate that provides it. However, thisnoncircular forms additional constraint which again limits the surfaceavailable for support. Furthermore, the angles of this shape themselvesform fragile zones, which only ensures low sturdiness to this stopoperation in rotation.

In other variants, a collar protrudes from the nucleus and surrounds itin the space between the two plates. In its exterior part this collarwidens at a certain height along the axis of the spinal column towardseach of the plates, which forms two interior borders that may besupported on the exterior border of contact surfaces of these sameplates. However, this type of external peripheral stop presents certaindrawbacks, in particular in terms of obstruction.

In fact, the configuration of this collar represents considerablevertical obstruction (along the spinal column axis) and the contactsurfaces of the plates must also present a certain height to be able tostop this collar in translation. Furthermore, the peripheral shape ofthis type of stop also occupies considerable radial space, in particularin a section plane where the spinal column presents the smallest width,as in sagittal plane. Given the limited space available in the disc, orintervertebral, space, this obstruction may occupy a space that would beuseful for the configuration of the rest of the prosthesis, which maylimit the results in terms of kinematics or reliability.

Moreover, this type of external peripheral stop requires a nucleus withbiconvex shape to be used, to allow for provision of sufficient heightfor the contact surfaces of the plates to form an exterior border usableby this stop. Therefore, this type of stop is difficult to produce for anucleus presenting one or more concave surfaces, while such forms ofnucleus may allow the kinematics of the prosthesis to be made morecomfortable with use by the patient.

In the case where the contact surfaces between nucleus and plates arenot circular, such a collar may also be able to limit the clearance inrotation of the nucleus relative to the plates, for example byperipheral contact between two concentric ellipses and with differentradii. However, such contact is done according to a very tight anglebetween the surfaces being supported on each other, which makes theposition of this limit not very precise and increases the risks of wearand tear or blockage by clamping. Furthermore, the clearance in rotationpermitted by such kinematics is directly dependent on the clearancepermitted in translation, and may not be chosen independently of thelatter during design of the prosthesis.

SUMMARY

A goal of the invention is to propose a prosthesis allowing the spinalcolumn better stability by a greater precision and sturdiness inrelative positions of pieces that compose it.

This goal is reached by a vertebral prosthesis device according to claim1.

Moreover to ensure stability of the spinal column after fitting such aprosthesis, the damages undergone by the spinal column because of thedifferent pathologies leading to deciding to fit a prosthesis sometimesmake useful the re-establishing of stability or posture that theelasticity of the spinal column no longer allows to be provided.According to the pathologies and the history of the patient, it may thenbe indicated to induce a certain angular correction in the configurationof the intervertebral space for example in the sense of lordosis or thatof kyphosis.

Certain types of existing prostheses use a variation in thickness of oneof the plates to induce such a correction. Such a correction is nothowever always very stable, in particular because the position ofsupports of the nucleus on the plates varies too much during movements.

Another goal of the invention is therefore to propose a prosthesisallowing the prosthesis better stability by the re-establishment ofposture adapted to the kinematics of movements that it produces.

This goal is reached by a vertebral prosthesis device according to claim5.

Additional developments of the invention are described in the dependentclaims.

The invention with its characteristics and advantages will be moreclearly evident with reading the description made in reference to theattached drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an exploded view in perspective of a prosthesisaccording to the invention, in a version including a convex lower plateand providing a central and annular stop;

FIG. 2 represents an exploded sectional view of a prosthesis deviceaccording to the invention in the same variant;

FIG. 3 represents an exploded sectional view of the prosthesis deviceaccording to the invention in a variant including a nucleus with flatlower surface and lower plate presenting an annular stop;

FIG. 4 represents an exploded sectional side view of the prosthesisdevice according to the invention in a variant including a nucleus withconcave lower face, an added block and a lower plate with annular stop;

FIG. 6 a represents a sectional side view of the prosthesis deviceaccording to the invention in a variant with central, annular andincline stop, in maximum incline position;

FIG. 6 b represents a sectional side view of a prosthesis according tothe prior arts where the nucleus presents a fixed position;

FIG. 6 c represents a sectional side view of a prosthesis according tothe prior arts where the nucleus is movable and is ejected under theload during a force in the maximum incline position;

FIG. 5 represents a sectional exploded side view of the prosthesisdevice according to a variant including an added block allowing acentral stop to appear and a flat lower plate presenting an annularstop;

FIG. 7 represents a sectional side view of the prosthesis deviceaccording to a variant without annular stop and where the central stoppresents a vertical section in the form of a dovetail, in maximumincline position;

FIGS. 8 a and 8 b represent sectional side views of the prosthesisdevice according to the invention according to a variant with inclinedaxis, including an annular stop and a central stop incorporated in thecontact surface supporting the nucleus, in the case of a single piecelower plate and an added block, respectively.

FIG. 8 c represents a sectional side view in a sagittal plane of theprosthesis device according to the invention according to a variant witha corrective nucleus presenting two faces in which the contact surfacesare not parallel;

FIG. 9 a represents a perspective view of the prosthesis deviceaccording to the invention according to a variant with two stopsexterior to the nucleus, held in a housing between pillars integral withthe lower plate;

FIG. 9 b represents a perspective view of the prosthesis deviceaccording to the invention according to a variant with two stopsexterior to the nucleus, each holding a pillar integral with the lowerplate between its arms;

FIG. 10 represents a perspective view of a device according to theinvention for fitting such a prosthesis;

FIG. 11 represents a perspective view of a device according to theinvention for inserting such a prosthesis, in position during theintroduction laterally of the prosthesis between two vertebrae;

FIG. 12 represents a perspective view of an assembly tool with aninsertion guide according to an embodiment of the invention;

FIG. 13 represents a perspective view of a prosthesis according to theinvention, presented at the entrance of the insertion guide of theinvention;

FIG. 14 represents a perspective view of the instrumentation accordingto an embodiment of the invention when the prosthesis is ready to beimpacted in the disc space.

DETAILED DESCRIPTION

A prosthesis according to the prior art disclosed by the patent FR 2 659226, consisting of a concave upper plate (3AA) sliding on a nucleus(2AA) presenting a spherical upper cap (23M) itself immobilized in ahousing of the lower plate (1AA), is represented in FIG. 6 b; inhorizontal position and in maximum incline position. Because the centreof the sphere (csAA) providing the contact surface with the nucleus islocated outside this same upper plate (3AA), its incline is combinedwith considerable lateral displacement (d1). This displacement creates abreak in the continuity of the vertical profile of the vertebral columnwhich may hamper the overall functionality of the movement and riskdamaging the tissues surrounding the vertebrae, such as ligaments andspinal marrow, which may be immediately or in the long run.

A prosthesis according to the prior art disclosed by the patent FR 2 730159, represented in FIG. 6 c, consists of a movable nucleus with twospherical surfaces oriented in the same direction, that may be laterallydisplaced between two plates and may allow incline without lateraldisplacement. In the extreme position, however, the nucleus is only kepton the exterior side by the furthest border of the spherical surface ofthe upper plate. Since this edge itself is already raised, there is agreat risk that too high a vertical pressure or a horizontal parasiticforce causes ejection of the nucleus towards the exterior of theprosthesis, causing intense pain and risks of immediate damage for thetissues surrounding the vertebral column, such as ligaments or spinalmarrow.

In an embodiment represented in FIG. 6 a, a prosthesis according to theinvention consists of a lower plate (1) being articulated with an upperplate (3) around a nucleus (2) presenting two spherical sliding surfaceswith the same orientation on both faces. The lower surface (21) of thenucleus (2) is concave and slides on a complementary convex surface (12)provided by the upper face, known as internal, of the lower plate (1).The upper surface (23) is convex and slides on a complementary concavesurface (32) provided by the lower face, known as internal, of the upperplate (3). In this embodiment, the radius of the lower contact surface(21) of the nucleus (2) is a radius greater then that of its convexupper surface (23), the centres of the spheres providing its two contactsurfaces being located on the same axis of symmetry (d2) of these twosurfaces. On their side, the two plates present contact surfaces (12,32) the axes of symmetry (d12, d32) of which are perpendicular to theirexternal faces (10, 30). The horizontal displacement part of the nucleusin one direction, due to the rotation on the upper sliding surfacearound its centre (cs), is compensated by a rotation of the nucleus onits lower sliding surface around its centre (ci) which induceshorizontal displacement of the nucleus (2) and therefore of the centre(cs) of the upper sliding surface. The radii of the two spheresproviding these sliding surfaces (12, 21, 23, 32) are determined so asto modify the lateral displacement of the plates by comparison with eachother during their incline. In one embodiment, the radii of thesesliding surfaces (12, 21, 23, 32) may be chosen so that the movement ofthe plate is reduced to an incline accompanied with a possible verticalcomponent but without horizontal displacement of the upper platerelative to the lower plate.

To avoid any risk of ejection of the nucleus (2) during forces in theinclined position, the latter is kept in its clearance by a centralstop: formed for example by a cylindrical block (4) protruding from theconvex surface of the lower plate and cooperating with edges of a recess(22) arranged in the centre of the contact surface (21) of the lowerconcave surface of the nucleus.

In one embodiment (FIG. 6 a) the lower plate also presents on its upperface an approximately cylindrical cavity (11) in which the edges (112)protrude from the contact surface (12) with the nucleus (2), andcooperate with the approximately cylindrical perimeter (20) of thisnucleus to ensure an operation of annular stop for it while limiting itsmovement towards the exterior of the contact surface (12) that providesit.

In one embodiment (FIG. 6 a) the internal surfaces of the plates, ontheir parts (113, 331) exterior to the sliding surfaces, present a formcapable of cooperating among themselves to limit by stop the incline ofthe plates with each other at a determined angle (a1).

In one embodiment represented in FIG. 7, the stop (4) is provided by theconvex surface (12) of the lower plate (1) and presents approximatelythe shape of an inverted cone, that is, its section is greater in itsend (42) opposite the surface (12) that provides it. By presenting anundercut shape, the interior surface (224) of the recess (22) cooperateswith the exterior surface (40) of the stop (4) to limit the raising ofthe nucleus when the latter is in furthest position against this stop(4).

According to the criteria connected for example to the resistance of thematerials, to the wear and tear or to the kinematics sought, thedifferent shapes and dimensions intervening in the stop mechanisms, forexample exterior (FIGS. 9 a and 9 b), annular, central or incline, couldbe determined so as to coordinate the order of arrival at stop of thedifferent parts. These shapes and dimensions could be determined forexample, so that the pieces reach stop at the same stage of movement,for example determined by angular incline (a1) between the lower (1) andupper (3) plates.

In an embodiment illustrated in FIGS. 7 and 8 a, the annular stopoperation is used very little or not at all, which allows the verticalobstruction of the prosthesis to be decreased.

In an embodiment presented in FIG. 3, the lower surface (21 a) of thenucleus (2) may be approximately flat, and then slide on a contactsurface (12 a) of the lower plate (1), also approximately flat. In thisembodiment, the flatness of the contact surface (12 a) of the lowerplate allows the edges (112) of this plate that protrude from thissurface to be particularly effective in their role of annular stop.Therefore, it is possible to manage without the central stop and thus toincrease the common contact surface between the lower plate and thenucleus, which on the one hand, decreases the wear and tear of thepieces and on the other hand, the risk of marking the surface of theplate with placement of the contour of the recess (22, FIG. 6 a) inwhich is accommodated the central stop (4, FIG. 6 a) in otherembodiments.

In an embodiment represented in FIG. 4, the lower plate (1) presents anapproximately cylindrical cavity (11) on its upper face the flat bottom(15) of which receives an intermediate piece called block (5). Thispiece is immobilized in the cavity (11) for example by the edges (112)of this cavity and presents on its upper face a convex surface (52) onwhich the lower concave surface (21) of the nucleus slides. Thisembodiment with the convex surface (52) on which the nucleus slides forexample allows the good qualities of the surface necessary for thefluidity of movement and longevity of the prosthesis to be obtained moreeasily and at less cost. It also allows several models to be providedwith blocks (5), of different shapes or qualities, that can be chosen inadvance or at the time of the surgery according to applications with thesame model of lower plate.

In an embodiment represented in FIG. 5, the lower plate (1) receives ablock (5) in an approximately cylindrical cavity (11) presenting avertical perforation that the stop (4) integral with the lower platecrosses. On its upper surface, this block supports a convex surface(52), on which the nucleus (2) and upper plate stack rests.

As a variant, the stop (4) may be integral with the block (5) on itsconvex contact surface (52)(FIG. 8 b).

Within the goal of obtaining at rest a corrective effect of the relativeposition of two vertebrae, the prosthesis may be produced in a variantwhere the axes of symmetry of the contact surfaces (12, 15, 52, 21, 23,32) or support (10, 30) of one or more pieces are not merged. Thepressure (F) exerted by the vertebrae on the two plates in thedirections perpendicular to their external surfaces (10, 30) will thenhave the tendency to induce and continuously maintain an incline (a3,FIGS. 8 a, 8 b et 8 c) between these plates (1, 3), that is not zero,for example in the sense of lordosis.

An embodiment of such a variant is represented in FIG. 8 a where theaxis of symmetry (d12) of the contact surface (12) of the lower plate(1) forms an angle (a2) determined with a direction (d10) perpendicularto the external surface of this same lower plate, while the axis ofsymmetry (d32) of the internal contact face (32) of the upper plate (3)is perpendicular to the external surface (30) of this same upper plate(3). The lower contact surface of the upper plate (3) presents an axisof symmetry parallel to a direction perpendicular to the support surface(30) of the ¶ of this same upper plate (3).

In another variant according to the same principle represented in FIG. 8b, a device is used that includes a lower plate (1) providing a block(5) the upper contact surface of which (52) presents an axis of symmetry(d52) forming an angle (a2) determined with a direction (d51)perpendicular to its lower face (51). The internal contact surfaces (15,32) of the lower (1) and upper (3) plates present axes of symmetryperpendicular to the support surface (10, 30) of their respectiveexternal faces. Thus, at the time of the surgery it is possible tochoose between several blocks (5) with different inclines, according tothe desired degree of correction. This block (5) could be maintainedfixed around an axis perpendicular to the lower plate (1) by any knownmeans (not represented) such as wedge, grooves or complementaryaccidents of shape between the block (5) and the lower plate (1) thatprovides it.

In another variant according to the same principle, represented in FIG.8 c, it is the nucleus (2) that presents two contact surfaces (21, 23)the axes of symmetry of which (d21, d23) form a determined angle (a2)between them. The internal contact surfaces (12, 32) of the lower (1)and upper (3) plates present axes of symmetry perpendicular to thesupport surface (10, 30) of their respective external faces. The angularcorrection (a3) induced by the nucleus (2) could then be kept constantlyin the desired direction relative to the body of the patient by arotation stop mechanism (not represented in FIG. 8 c) of this samenucleus, such a mechanism being described later (FIGS. 9 a and 9 b).

In one embodiment the device according to the invention presents anexterior stop mechanism, located outside the perimeter of the contactsurfaces of the nucleus (2).

In a variant represented in FIG. 9 a, this mechanism is formed of twoprotruding parts (6) protruding from the cylindrical exterior surface ofthe perimeter of the nucleus (2) in opposite directions. Each of theseprotruding parts is held in a housing (162) delimited by two pillars(161) integral with the lower plate (1). These pillars cooperate withthe protruding part (6) or with the surface (20) of the perimeter of thenucleus or both for limiting the movements of this same nucleus intranslation as in rotation parallel said plate. The housing issufficiently large to allow small displacements of the nucleus requiredfor the kinematics of the device, while being sufficiently narrow sothat this same nucleus and the lower plate are adjacent in certainpositions, for example, positions of maximum incline of the spinalcolumn. The protruding part (6) or perimeter surface (20) of the nucleus(2) then cooperates with the pillars (161) of the lower plate to retainthis same nucleus and avoid any lateral ejection.

The pillars (161) present a larger section at the end than at the base,thus limiting the raising of the nucleus.

In another operating variant according to the same principle andrepresented in FIG. 9 b, this mechanism is formed of two protrudingparts (6) protruding from the cylindrical exterior surface (20) of theperimeter of the nucleus (2) in opposite directions. Each of theseprotruding parts presents two arms delimiting a housing (66) which holda pillar (163) integral with the lower plate (1). The pillars (163)present a larger section at their end than at their base.

These embodiments of stop (9 a and 9 b) may allow the central stop to bedisposed of and to thus increase the contact surfaces which decreasesthe wear and tear. These types of stop (6) are also particularlyvaluable because of the limitation of the movements of the nucleus inrotation along an axis approximately parallel to the axis of the spinalcolumn. In fact, this limitation makes it possible to use a correctivenucleus in which the contact surfaces present axes of symmetry that arenot parallel, while maintaining in them the correction in a constantdirection relative to the body of the patient.

In an embodiment represented in FIG. 6 a, the lower (1) and upper (3)plates receive means for bony anchoring on their external face, designedto immobilize tile prosthesis between the vertebrae or adjacent elementsof the spinal column. These anchoring means may be pins (8) or wingspresenting a small cross section at their end away from the plate thatprovides them. These pins then are embedded or are impacted by punchingin the material of the bony elements (V) between which the prosthesis isfitted, for example under the effect of the pressure exerted by theligaments when the tools are withdrawn, the tools that kept thevertebrae separated. Driving in the pins in the material of the bonyelement (V, FIG. 6) then prevents the prosthesis from sliding outsideits site.

In an embodiment represented in FIG. 1, the plates (1, 3) present one ormore accidents of shape such as notches (7) or perforations (notrepresented) enabling catching of a grasping tool to remove theprosthesis from its site in case of need. The lower plate (1) presents aconvex upper contact surface (12) providing a central stop (4) and acavity presenting edges (112) forming an annular stop.

In an embodiment represented in FIG. 10, an insertion device accordingto the invention is presented in the form of an element (9) calledinsertion guide, presenting an internal channel (90) approximatelyrectangular in section in which the prosthesis (P) can slide. Thischannel (9) is formed from two semi-guides (91, 92) with a cross sectionin the shape of a “U”, arranged inversely and fitted into each other. Atone of the ends, this guide (9) presents one or more parts calledsupport blocks or edges (910, 920) protruding along its longitudinalaxis (d9). These support blocks (910, 920) form an extension of thewalls of the channel called vertical (9) that form the small sides ofthe rectangular section of the channel (9).

In an application method illustrated in FIGS. 10 and 11, the fitting ofthe prosthesis device according to the invention is carried outaccording to the following steps:

separating the vertebrae with the aid of known instruments, for exampledistraction tools;

sliding the insertion guide (9)around the distraction tools so as tointroduce the support edges (910, 920) between the vertebrae (V);

release and extraction of the distraction tools, the vertebrae beingkept spread apart by the support edges of the insertion guide;

introduction of the prosthesis ready for fitting into the channel, andsliding to near the spinal column;

adjustment of the incline of the prosthesis according to conformation ofthe space available between the vertebrae with possible separating ofthe two parts (91, 92) of the channel according to a corresponding angle(a9) to help with this adjustment;

positioning of the prosthesis in the intervertebral space by pushing bythe interior of the channel;

extraction of the support blocks (910, 920) of the channel outside theintervertebral space and impacting blocks for bony anchoring in thevertebrae (V).

In an embodiment illustrated in FIGS. 12 a to 14, the instrumentationused for fitting the prosthesis according to the invention comprises aninsertion guide (93) provided with an internal channel (90). Thischannel (90) presents an approximately rectangular cross section, orwith a shape approximately complementary to the exterior profile of theprosthesis. This internal channel (90) is provided with dimensions andshape adequate for allowing the prosthesis to pass and to guide from oneof its ends to the other, in a position and along a displacementapproximately parallel to the external faces of its plates (1, 3).According to the applications, the channel (90) of the insertion guide(93) may include scallops in its walls opposite plates of theprosthesis. Such scallops make it possible to allow the anchoring means(8, 81) to pass provided by the plates of the prosthesis, while guidingthe latter sufficiently precisely in the channel. In the embodimentillustrated here these scallops have the shape of grooves (934, 936)along the axis (d9) of the channel provided by the internal walls of thechannel opposite plates (1, 3).

At one of its ends, called the working end, the walls (931, 932) of thechannel (90) perpendicular to the plates of the prosthesis, that is,located in the plane containing the axis of the spinal column, areextended along the axis (d9) of this channel over a distance determinedso as to protrude relative to the walls of this same channel that areparallel to the plates of the prosthesis. Since these extensions thusform the protruding parts, or support edges, that may be inserted in theintervertebral space to maintain the separation of the plates from thetwo vertebrae surrounding this space.

The height of these support edges (931, 932) is determined so as tomaintain adequate space for allowing the introduction of the prosthesisand its anchoring means (8, 81), according to the method of anchoringprovided. If the anchoring means are formed from sockets (8) or wings(81) before being introduced freely in the space, the support edges willhave sufficient height to allow the height of these sockets or wings topass. If the anchoring means are formed from wings having to penetratethe vertebral plates by a hollowed trench in the surface of these platesand opening laterally, the height of these support edges could besufficiently low to allow the height of the prosthesis to pass but notthe wings.

During surgery for fitting such a prosthesis, the surgeon begins byremoving the vertebral disc or its debris, and then uses distractiontools to increase the disc space available between the two vertebraehaving to receive the prosthesis. Such tools are often formed with anelongated handle providing a flat part at the end. This flat end isintroduced between the vertebrae, then it is made to pivot to increasethe separation of the vertebrae.

In the instrument according to the invention, the internal channel (90)of the insertion guide (93) is provided to be able to be threaded aroundsuch distraction tools, once they are in place between the vertebrae.Once brought near the spinal column while surrounding the distractiontools, the insertion guide is pushed so as to introduce its edges (931,932) between the vertebrae, in a plane approximately parallel to thespinal column. The distraction tools may then be removed from the spinalcolumn by making them slide in the channel (90) of the insertion guide,while the height of the support edges preserves sufficient space betweenthe vertebrae to allow fitting of the prosthesis. In the embodimentillustrated here, the insertion guide (93) presents means forinterlocking with a guide assembly tool (94), used to bring it near thespinal column and facilitating its fitting. This guide assembly tool(94) is also usable for removing the insertion guide and its supportedges, and allowing the vertebrae to tighten on the prosthesis, once thelatter is in place.

Such a guide assembly tool (94) is illustrated in FIGS. 12 a and 12 b.This tool (94) consists of two elongated tubes (941, 946) articulated toeach other by means (945) located at one end, called assembling, of thistool. These two elongated tubes at their end located opposite theassembling end, each provide interlocking means for insertion guide(93). These interlocking means may comprise, for example, a hook (942,947) on each tube (941, 946) the opening of which is located oppositethe other tube. When the guide assembly tool (94) is approached by theinsertion guide (93), the fact of tightening the tubes to each otheraround their articulation makes it possible for each hook (942, 947) totightly encircle a tongue (934, 936) in the shape of a “T” protruding oneach groove (933, 935) of the insertion guide. Within and in the axis ofeach tube (941, 946) is found a rod (943, 948) that may be displacedlongitudinally relative to the tubes by screwing means comprising ascrewing wheel (944, 949). The screwing of these wheels causes theadvance of the rod in the tube and the end of the rod opposite thescrewing wheel then comes to lean and block the tongue (934, 936) of theinsertion guide (93) within the hook (942, 947) provided by the tubereceiving this same rod, This blockage thus makes it possible tointerlock the guide to its assembling tool sufficiently stably to makeit possible to position said guide around the distraction tools at thespinal column.

These means (934, 936) of interlocking the insertion guide (93) orothers provided by said insertion guide also make it possible to guideand interlock means of approach (95) to this insertion guide. Thesemeans (95) of approach include means for positioning the prosthesis,these means of positioning being provided to position and maintain theassembled prosthesis in a determined position relative to these means(95) of approach even in the absence of the insertion guide (93). Thispositioning of the prosthesis on the approach means makes it possiblefor the interlocking of tie approach means and the insertion guide toput the prosthesis in a position making it possible for it to be easilydisplaced from these same means or approach up to in the internalchannel (90) of the insertion guide (93). Thus, it is possible toprepare the prosthesis in the approach means (95) independently of therest of the operation. Then it is possible to fit the insertion guide onthe spinal column without being preoccupied with the prosthesis, theneasily and rapidly inserting this prosthesis in the insertion guide (93)while the latter is already in position against the spinal column.

As well as illustrated in FIG. 14, these approach means (95) include twoshafts (951, 952) connected to each other by articulation (955) so as tocome to pinch the prosthesis (P) between two flattened parts ensuring adetermined position of the prosthesis relative to these approach means.The ends of these shafts opposite the articulation includinginterlocking means (953, 954) capable of cooperating with theinterlocking means (934, 936) of insertion guide (93) to ensure adetermined position of approach means (95) relative to the insertionguide (93) as well as certain stability to this assembly. At the end ofeach shaft (951, 952), these interlocking means (953, 954) may inparticular comprise a scalloping in which the arms come to encircle theexterior of the groove (933, 935) of the insertion guide while glidingunder the upper bar of the “T” formed by the tongue (934, 936) providedby this same insertion guide.

Once the insertion guide (93) fitted instead of the distraction toolsand the approach means (95) interlocked to this guide, the prosthesis istherefore in a stable position relative to the spinal column, and may beinserted in the insertion guide then slide up to the disc space. Thisdisplacement is achievable here with the aid of impacting means, orimpactor (96) comprising an impacting end capable of pressing on theassembled prosthesis, distributed on both plates and without touchingthe nucleus. This impactor includes a central elongated part (960) thatcan be inserted in guiding means as an opening in the shape of a “U”provided by approach means (95) at their articulated end (955). Thisimpactor includes another end (962) called assembling or striking, thatcan act to apply a continuous pressure or repeated shocks, with the handor by any known tool or apparatus. Such an action, applied on theassembling end (962) of the impactor in the axis (d9) of the channel(90) then will be reverberated by the end (961) on the prosthesis, so asto cause its entrance then sliding in the channel (90) of the insertionguide (93), then its insertion or impaction in the intervertebral space.

In all the prosthesis devices according to the invention described here,it is necessary to understand that the distinctions of “lower plate”(represented on the bottom of the figures and referenced 1) and “upperplate” (represented on the top of the figures and referenced 3) areabove all conventional, the device being able to be used in a differentposition, even inverse of that consisting of placing the lower platetoward the bottom of the vertebral column.

Thus, the invention proposes an intervertebral disc prosthesis devicecomprising at least three pieces, which parts include a plate (1) calledlower and a plate (3) called upper (3) producing around at least oneintermediate part called nucleus (2) an articulation by support orsliding between loadbearing surfaces (12, 15, 21, 23, 32) of saidpieces, one of these pieces including at least one protruding part oraccident of shape cooperating with the shape of at least one other ofsaid pieces to form an stop limiting the possibilities of movement ofthe nucleus, characterized in that this stop operation uses at least onestop external to the loadbearing surfaces comprising at least one part(161, 163) protruding from at least one plate (1), located outside theloadbearing surface (12, 15) of said plate and including a face directedtowards the interior of the prosthesis, this face cooperating with aperipheral part (6) of the nucleus (21, 23) situated outside itsloadbearing surfaces (21, 23) and in which the surface is directedtowards the exterior of the nucleus, to limit displacements of thenucleus in translation or in rotation or both in a plane approximatelytransverse to the spinal column.

According to a particular aspect, the loadbearing surfaces (21, 21 a,23) of the nucleus (2) in contact with the lower plate (1) and upperplate (3) present axes of symmetry (d21, d23, respectively) formingbetween them a determined angle (a2) that is not zero, so that apressure (F) exerted on the two plates (1, 3) along directionsperpendicular to their external surfaces induces an incline (a3) ofthese plates with each other.

According to a particular aspect, this external stop limits themovements in rotation of the nucleus (2) relative to at least one plate(1) by contact between parts (6, 161, 163) supporting each other by stopsurfaces, this support being done along a direction approximatelyparallel to the normal of each of these stop surfaces.

According to a particular aspect, the external stop includes a tongue(6) protruding form the nucleus (6) which cooperates with one of theplates (1) by confining this tongue (6) in a housing (162) delimited bypillars (161) protruding from the internal race of this same plate(1) orby a recess (66) separating this tongue into two arms encircling apillar (163) protruding from the internal face of this same plate (1),the internal face of a plate being defined at that oriented on the sideof the nucleus.

According to a particular aspect, the end of at least one pillar (161,162, 163) presents a section greater than its base, this enlargement ofthe pillar cooperating with the shape of the external stop tongue (6) ofthe nucleus (2) to limit the raising of this same nucleus relative tothe plate (1) providing this pillar.

In the same spirit, the invention also proposes an intervertebral discprosthesis device comprising at least three pieces, including a plate(1) called lower and a plate (3) called upper (3) producing around atleast one intermediate element called nucleus (2) an articulation bysupport or sliding between loadbearing surfaces (12, 15, 21, 23, 32) ofsaid parts, one of these parts including at least one protruding part oraccident of shape cooperating with the shape of at least one other ofsaid pairs to form an stop limiting the possibilities of movement of thenucleus, characterized in that the loadbearing surfaces (21, 21 a, 23)of the nucleus (2) in contact with the lower plate (1) and upper plate(3) present axes of symmetry (d21, d23, respectively) forming betweenthem a determined angle (a2) that is not zero so that a pressure (F)exerted on the two plate (1, 3) along directions perpendicular to theirexternal surfaces induces an incline (a3) of these plates with eachother.

According to a particular aspect this device is characterized in thatthe operation of the stop uses at least one stop external to theloadbearing surfaces comprising at least one part (161, 163) protrudingfrom at least one plate (1) located outside the loadbearing surface (12,15) of said plate and including a face directed towards the interior ofthe prosthesis, this face cooperating with a peripheral part (6) of thenucleus located outside its loadbearing surfaces (21, 23) and in whichthe surface is directed towards the exterior of the nucleus, to limitthe displacements of the nucleus in translation or in rotation or bothin a plane approximately transverse to the spinal column.

According to a particular aspect, when the two plates have theirexternal faces (10, 30) parallel to each other, their loadbearingsurfaces (12, 12 a, 32) cooperate with the loadbearing surfaces (21, 21a, 23) of the nucleus (2) present axes of symmetry (d1 2, d32) forming adetermined angle (a4) between them so that a pressure (F) exerted on thetwo plates (1, 3) along directions perpendicular to their external facesinduces an incline (a5) of these plates with each other.

According to a particular aspect, the loadbearing surfaces (12, 32)provided by the internal face of the lower plate (1) and the internalface of the upper plate (3) are each in complementary contact with asupporting surface (21, 23, respectively) of the nucleus (2), and eachpresent a shape, convex and concave, respectively, or inversely, thisnucleus itself presenting a perimeter (20) approximately cylindricalalong the axis of symmetry of its contact faces (21, 32).

According to a particular aspect, the internal face of the lower plate(1) presents a loadbearing surface (12 a) cooperating with a loadbearingsurface (21 a) of the lower face of the nucleus (2), this same nucleusincluding on its upper face a convex loadbearing surface (23) incomplementary contact with a concave loadbearing surface (32) of theinternal face of the upper plate (3) the loadbearing surface (12 a) ofthe internal face of the lower plate being sufficiently extended toallow movement of the nucleus relative to this same lower plate.

According to a particular aspect, an intermediate element called block(5) is added on the internal face of one (1) of the plates and producesan articulation with the other plate (3) around the nucleus (2) whichnucleus presents a concave loadbearing surface (21) and a convexloadbearing surface (23) these two loadbearing surfaces being in contactin a complementary way with one loadbearing surface (52) of the block(5) one, and with a loadbearing surface (32) of the internal face of theplate (3) not including block, for the other.

According to a particular aspect, the axis of symmetry (d52) of theconvex loadbearing surface (52) of the block (5) forms a determinedangle (a4) with an axis (d51) perpendicular to its surface (51) withcontact of the plate (1) so that a pressure (F) exerted on the twoplates (1, 3) along directions perpendicular to their external facesinduces an incline (a5) of the plates with each other.

According to a particular aspect, at least one of the loadbearingsurfaces (12, 52, 21, 23, 32) allowing articulation has a shape makingup part of a sphere.

According to a particular aspect, the loadbearing surfaces of the twofaces of the nucleus (2) have shapes making up parts of a sphere, theface presenting a concave loadbearing surface (21) having a radiusgreater than that of the face presenting a convex loadbearing surface(23).

According to a particular aspect, each of the plates (1, 3) includes onits external face one or more protruding parts with small sectionforming a bony anchoring, these protruding parts coming to be embeddedor impacted in the surface of contiguous bony elements (V) under theeffect of pressure, once the prosthesis is in position between twovertebrae or bony elements.

According to a particular aspect, one or more of the pieces of theprosthesis include accidents of shape, notches (7) or perforationslikely to see a tool again to facilitate the extraction of saidprosthesis.

According to a particular aspect, the plates (1, 3) are composed of analloy with base of stainless steel with cobalt-chromium and the nucleus(2) has polyethylene base.

In the same spirit, the invention proposes instrumentation for insertingor fitting the prosthesis according to one of claims 1 to 15characterized in that it comprises an insertion guide (9,93) includingan internal channel (90) presenting an end in which certain edges orsupport edges (910, 920, 931, 932), protrude from the others along thelongitudinal axis (d9) of the channel so as to be able to take the placeof distraction tools of a known type previously used to increase theopening of the disc space, this channel (90) presenting an internalsection capable of surrounding these same distraction tools while theymaintain this opening, then allowing their extraction through saidchannel while said support edges (910, 920, 931, 932), for their part,preserve the opening of the disc space by replacing the distractiontools, then receiving and guiding the prosthesis (P) for insertion inthis disc space.

According to a particular aspect, the internal channel (90) presents anapproximately rectangular section or with a shape approximatelycomplementary to the exterior profile of the prosthesis, taken in asection along the plane perpendicular to the direction of insertion.

According to a particular aspect, the support edges (931, 932) ofinsertion guide (93) form an extension of the channel (90) walls locatedon a plane containing the axis of the spinal column.

According to a particular aspect, the insertion guide (9) is formed fromat least two elements (91, 92) separated along one or more planesparallel to the longitudinal axis (d9) of the channel, these parts eachincluding at least one portion of the transverse section of the channeland being able to be spread apart according to a determined angle (a9)and allowing the introduction and sliding of the prosthesis (P) in thechannel.

According to a particular aspect, the internal surface of the channel(90) on its walls opposite external faces of the plates (1, 3) of theprosthesis (P1), includes at least one groove (913, 914) allowing thepassage of protruding parts (8, 81) for anchoring provided by theseplates during displacement of the prosthesis in this channel (90).

According to a particular aspect, the instrumentation comprises approachmeans (95) of the prosthesis capable of receiving the prosthesis and ofmaintaining with it all the different components, these approach means(95) being able to be connected by interlocking means to the insertionguide (93) so as to present the prosthesis at the entrance of thechannel (90) in a position appropriate for allowing its entrance intothis channel (90).

According to a particular aspect, the instruments comprises insertionmeans, called impactor (96) of the prosthesis in the channel (90) of theinsertion guide (93) then into the disc space, this impactor beingguided by the support means (95) so as to be in contact with theprosthesis in its part opposite the entrance of the channel (90), thisimpactor (96) being able to apply or transmit a pressure or repeatedshocks to the prosthesis to cause its sliding in the channel, then itsinsertion in the disc space.

According to a particular aspect, the support means include two shafts(951, 952) connected by an axis to a assembling end (955), these shaftsbeing able to be closed up to pinch the prosthesis (P) between them andto maintain it so assembled, these two shafts each providing connectionmeans to the guide for use (93), this connection then maintaining thesetwo shafts closed up on the prosthesis.

It must be obvious for those skilled in the art that the presentinvention allows embodiments in numerous other specific forms withoutgoing far from the field of application of the invention as claimed. Asa result, the present embodiments must be considered by way ofillustration, but may be modified in the field defined by the scope ofthe attached claims, and the invention must not be limited to detailsgiven above.

1 . A method of surgically inserting an intervertebral prosthesisbetween two adjacent vertebrae comprising the steps of: separating twoadjacent vertebrae to form a gap between the two adjacent vertebrae;placing at least one support block at least partially into the gap;maintaining the gap with the support block; introducing theintervertebral prosthesis into a channel formed by an insertion guide;moving the intervertebral prosthesis through the channel; positioningthe intervertebral prosthesis in the gap; and removing the supportblock.
 2. The method of claim 1 in which the step of moving theintervertebral prosthesis comprises a step of adjusting a first angle ofincline associated with two opposing plates of the intervertebralprosthesis by adjusting a second angle of incline between twosemi-guides.
 3. The method of claim 1 in which the at least one supportblock comprises two support blocks formed by extensions of opposinglateral sides of a semi-guide.
 4. The method of claim 3 in which thestep of placing the at least one support block comprises placing the twosupport blocks at least partially into the gap around a distractiontool.
 5. The method of claim 4 further comprising a step of removing thedistraction tool through the channel.
 6. The method of claim 1 in whichthe intervertebral prosthesis comprises plates and a nucleus, and thestep of moving the intervertebral prosthesis through the channelcomprises providing an insertion tool and using the insertion tool topush the plates of the intervertebral prosthesis without contacting thenucleus of the intervertebral prosthesis.
 7. The method of claim 6 inwhich the insertion tool provided is an impactor.
 8. The method of claim1 in which: the insertion guide comprises two semi-guides and the atleast one support block comprises support edges disposed at an end ofone of the semi-guides; the step of placing at the least one supportblock at least partially into the gap comprises placing at least a partof the support edges into the gap; and the step of maintaining the gapwith the support block comprises using the support edges to keep thevertebrae apart.
 9. A method of surgically inserting an intervertebralprosthesis between two adjacent vertebrae comprising the steps of:separating the adjacent vertebrae to form a gap between the adjacentvertebrae; moving at least one support block of an insertion guide intothe gap; placing the intervertebral prosthesis in a channel in theinsertion guide; moving the intervertebral prosthesis along the channeltoward the gap; positioning the intervertebral prosthesis in the gap;and removing the support block of the insertion guide from the gap. 10.The method of claim 9 in which the support block comprises two supportblocks formed by extensions of opposing lateral sides of the insertionguide.
 11. The method of claim 10 in which the step of separating theadjacent vertebrae comprises using a distraction tool and the step ofmoving the at least one support block comprises moving the two supportblocks of the insertion guide around the distraction tool, the methodfurther comprising the step of removing the distraction tool along thechannel.
 12. The method of claim 9 in which the step of moving theintervertebral prosthesis along the channel comprises using at least onescallop of the insertion guide to guide at least one anchor on theintervertebral prosthesis.
 13. The method of claim 12 in which the stepof positioning the intervertebral prosthesis in the gap comprises movingthe at least one anchor into a trench formed in at least one of thevertebrae.
 14. The method of claim 9 in which the step of moving theleast one support block into the gap or the step of removing the supportblock from the gap, or both, are performed using an assembly tool havingat least one interlocking part which interlocks with the insertionguide.
 15. The method of claim 9 in which the step of placing theintervertebral prosthesis in a channel in the insertion guide isperformed at least in part using an elongated support having at leastone interlocking part which interlocks with the insertion guide.
 16. Themethod of claim 15 in which the step of moving at least one supportblock into the gap or the step of removing the support block, or both,comprise using the elongated support.
 17. A method of surgicallyinserting an intervertebral prosthesis between two adjacent vertebraecomprising the steps of: providing an insertion guide having a first anda second longitudinal element each having a support block configured tosupport one of the adjacent vertebrae and a pathway between the firstand the second longitudinal elements configured for passage of theintervertebral prosthesis into a gap formed between the two adjacentvertebrae; supporting the vertebrae with the support blocks of the firstand second longitudinal elements; placing an impactor between the firstand second longitudinal elements; and using the impactor to move theintervertebral prosthesis along the pathway into the gap.
 18. The methodof claim 17 in which the insertion guide further comprises anarticulation of the first and second longitudinal elements.
 19. Themethod of claim 18 in which the articulation comprises a pivot.
 20. Themethod of claim 17 in which the insertion guide further comprises aguide for the impactor the guide located proximate to the articulation,and the step of placing the impactor between the first and secondlongitudinal elements comprises inserting the impactor in the guide. 21.Instrumentation for surgically inserting an intervertebral prosthesis ina gap between two adjacent vertebrae comprising: an insertion guidehaving a longitudinal axis and comprising an end having an openingthrough which the intervertebral prosthesis may pass and through which adistraction tool may be received; a channel arranged and configured forpassage along the longitudinal axis of the intervertebral prosthesis andthe distraction tool; and edges protruding from the end along thelongitudinal axis, the edges configured and arranged to maintain the gapduring insertion of the intervertebral prosthesis.
 22. Instrumentationof claim 21 in which the channel has an approximately rectangular crosssection that is approximately complementary to the exterior profile ofthe prosthesis.
 23. Instrumentation of claim 21 in which the edges areformed by extensions of walls of the channel.
 24. Instrumentation ofclaim 21 further comprising plural elements forming the channel, whichelements are adjustable to form a determined angle.
 25. Instrumentationof claim 21 in which at least one surface of the channel has a grooveconfigured and arranged for passage of an anchor of the intervertebralprosthesis.
 26. Instrumentation of claim 21 further comprising a supportconfigured to hold the intervertebral prosthesis stable during approachto the channel.
 27. Instrumentation of claim 26 further comprising animpactor cooperating with a guide of the support, the impactor having astriking end configured for application of a force and an impacting endconfigured to transmit the force to the intervertebral prosthesis. 28.Instrumentation for surgically inserting an intervertebral prosthesisbetween two adjacent vertebrae comprising an insertion guide comprisingplural semi-guides forming a channel along a longitudinal axis of theinsertion guide, at least one semi-guide having plural support blocks.29. Instrumentation of claim 28 in which the support blocks compriseedges of extensions of walls of the at least one semi-guide havingplural support blocks.
 30. Instrumentation for insertion of anintervertebral prosthesis into a space between adjacent vertebraecomprising: a first and a second longitudinal element each having asupport block configured to support one of the adjacent vertebrae; apathway between the first and the second longitudinal elementsconfigured for passage of the intervertebral prosthesis into the spacebetween the adjacent vertebrae; and an impactor configured to move theintervertebral prosthesis along the pathway into the space between theadjacent vertebrae.
 31. Instrumentation of claim 30 further comprisingan articulation of the first and second longitudinal elements. 32.Instrumentation of claim 31 in which the articulation comprises a pivot.33. Instrumentation of claim 30 further comprising a guide for theimpactor, the guide located proximate to the articulation. 34.Instrumentation for surgically inserting an intervertebral prosthesis ina gap between two adjacent vertebrae comprising an insertion guidecomprising: a longitudinal axis; an end having an opening through whichthe intervertebral prosthesis may pass and through which a distractiontool may extend; a channel arranged and configured for passage along thelongitudinal axis of the intervertebral prosthesis and the distractiontool; and vertebral support walls of the channel configured to supportthe adjacent vertebrae during insertion of the intervertebralprosthesis.
 35. Instrumentation of claim 34 in which the channelcomprises scallops configured and arranged to permit passage of ananchor of the intervertebral prosthesis.
 36. Instrumentation of claim 34further comprising an assembly tool having at least one interlockconfigured for engagement with a cooperating interlock of the insertionguide.
 37. Instrumentation of claim 36 in which the interlock of theassembly tool comprises a hook and the interlock of the insertion guidecomprises a tongue.
 38. Instrumentation of claim 36 in which a rodoperates the interlock of the assembly tool.
 39. Instrumentation ofclaim 36 in which the assembly tool comprises at least one tube. 40.Instrumentation of claim 34 further comprising a support configured toposition and support the intervertebral prosthesis during its approachto the gap.
 41. Instrumentation of claim 40 in which the supportcomprises shafts connected by an articulation.
 42. Instrumentation ofclaim 40 in which the support has positioners configured to stabilize anassembled intervertebral prosthesis during its approach to the gap. 43.Instrumentation of claim 42 in which the positioners are flattened partsdisposed along shafts of the support.
 44. Instrumentation of claim 40 inwhich the support comprises an interlock configured to engage acomplementary interlock of the insertion guide.
 45. Instrumentation ofclaim 44 in which the interlock of the support comprises a scallop andthe interlock of the insertion guide comprises a tongue. 46.Instrumentation of claim 34 further comprising an impactor having astriking end for the application of force and an impacting end fortransmitting the force to the intervertebral prosthesis. 47.Instrumentation of claim 46 in which the impacting end is configured andarranged to transmit the force to plates of the intervertebralprosthesis but not a nucleus of the intervertebral prosthesis. 48.Instrumentation of claim 46 in which impactor comprises an elongatedpart cooperating with a guide of a support.